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21 May 2001
Pulse of magma at Kilauea
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| Left: Tilt at Uwekahuna (upper two plots)
and Sand Hill (lower two plots) during inflation event of May 20, 2001. The tilt at Uwekahuna is shown
as radial
and tangential components relative to a center near Halemaumau. The tilt at Sand Hill is shown as E-W and N-S
components. Upward deflection indicates inflation at Uwekahuna and
deflation at Sand Hill. Note the rapid inflation for one hour and slower
decay thereafter. The tilt indicates the rapid rise of a pulse of magma
into the shallow summit reservoir and then a slower leakage into the east
rift zone. Right: Seismogram for the North Pit seismometer near
Halemaumau, for the 24-hour period starting at about 0830 on May 20. Note
the earthquake swarm and weak tremor in the morning and early afternoon,
followed by moderately strong volcanic tremor accompanying the inflation, followed in
turn by very few earthquakes and no tremor during the deflation. See large
images for best detail.
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Tilt record near Pu`u `O`o (upper two plots) and on northwest flank of Pu`u `O`o (lower
two plots) during event on May 20, 2001. Only slight inflation is indicated
in the top two plots. Pu`u `O`o cone itself shows sharp inflation, starting
20 minutes after summit inflation and recording a pressure pulse in the east
rift zone, followed by injection of magma below Pu`u `O`o and then movement
into hidden storage.
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| Two views showing how dark
pahoehoe resurfaced the inner "trough" of the crater floor of
Pu`u `O`o. Glowing areas are vents in the crater floor from which lava
upwelled on the night of May 20-21. These same vents alternately served as
drain holes that kept the level of ponded lava from rising more than a few
meters within the trough.
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Shiny pahoehoe in active flow overrides dark `a`a erupted in
1983-85. Above the B & B in Royal Gardens (red-roofed house at end of
road), the irregular surface of the `a`a helps keep the pahoehoe from moving
farther east. If the upslope pahoehoe overtops the `a`a, the B & B will
be in harm's way. View looks north beyond top of Pulama pali.
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23 May 2001
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Active bench at the southeast corner of the active flow
field at 0842. At least eight different streams of lava are falling into the
ocean. Can you see them all? You need the large view to find them.
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| Mid-afternoon views of a
3-m-high hornito that has developed near one of the breakout points between
2300 and 2240 feet. A hornito is a conical mound of spatter above a
rootless vent--in this case, a break in the roof of a lava tube. A hornito
is hollow but often roofed. Commonly, lava can be observed, through a hole
in the side or roof of the hornito, to be actively spattering. In the large close-up, note how the spatter has slopped out of the
top and run a short distance down the mound.
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| Left: Mid-afternoon view
of a skylight through thin roof of a lava tube near one of the breakout
points between Pu`u `O`o and the top of Pulama pali. Lava is bubbling at the left
(downstream) end of skylight. Right: Active pahoehoe flow from the 2200-foot breakout
point in the late-afternoon light. The lava toe nearest the camera is
advancing in a twisting roll.
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25 May 2001 and summer 1999
Shatter ring
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| "What in the world is a
shatter ring?" Several viewers have asked that question. A shatter
ring--a term recently coined at HVO and not explained or illustrated anywhere in
popular circles--forms when lava
pressure in a tube exceeds the strength of the overlying crust. Such a
condition happens if a tube is blocked downstream. The pressure uplifts the crust
at some weak point to form a tumulus. If this process
is repeated many times, the outer edges of the tumulus become broken or
shattered to form a shatter
ring. A shatter ring may have smooth pahoehoe inside its broken outer
ring. The presence of a shatter ring tells us that the underlying
tube has been pressurized many times. The two images above show two
different shatter
rings as they were forming in July and August 1999 on the flat below Pulama
pali. The shatter ring in the right image is the same as the one shown in
the aerial view below.
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Though impressive, shatter rings are small features on the
overall flow field. The one shown here--the brown feature in the lower
center of the image--is only about 50 m across and is dwarfed by its surroundings. Yet it stands apart
from the pahoehoe around it, and so this shatter ring is now used as a
landmark for hikers across the flow field, particularly those from the end
of Chain of Craters Road off the upper right part of the image.
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25 May 2001
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| Left: Steam rises from ocean entry in
early afternoon. Behind is the flow field, reaching all the way back to Pu`u `O`o (on skyline).
Smoke and fume define course of active flow along west side of field.
Swath of shiny pahoehoe next to green "Royal Gardens" kipuka is the recently active far
east flow. Right: View westward along Pulama pali, showing far east
flow (next to biggest forested area), a 1980's vintage `a`a flow beyond
(dark), and the recently active flow field farther west and south. Smoke rises from
burning vegetation along west margin of west flow.
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View southeastward from above Pu`u `O`o, showing the flow
field indented with many skylights and collapse pits from past lava-tube systems. Steam plume
from ocean entry is barely visible in distance, bent southwestward by
strong trade wind.
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| Left: Tangled fallen
trees along margin of recently active far east flow above Pulama pali.
Steam plume from ocean entry in background. White wood ash on the flow
surface is all that remains of burned wood. The ash doesn't last long,
washed by rain and blown by wind. Right: Burning wood imbedded in
surface of hot crusted flow. The wood will probably burn away completely,
leaving an impression in the surface of the flow.
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31 May 2001
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Dark pahoehoe (left), erupted in the past two weeks but
stagnant in this photo, encroaches on rugged gray `a`a erupted in 1985. Flow
direction is toward observer. View is of area 1-2 km above Pulama pali; Pu`u `O`o is in extreme upper left.
Levees on the `a`a are 2-3 m high, and
width of view is 300-500 m.
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| Left: Southeastward
view
looking obliquely down Pulama pali to coastal flat beyond. Fume rises from lava in hidden
tubes in foreground, smoke from fire along active pahoehoe in middle
ground, and wind-bent steam plume from eastern ocean entry in background. Right:
Looking north across margin of active pahoehoe breakout into Royal Gardens
subdivision. The intersection nearest the new flow is Prince Street at
Lehua Street. As the flow field on the coastal flat thickens, more and
more of the subdivision becomes inundated.
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Map of flows from Pu`u `O`o to the ocean: 22 March 2001
Large
map Map shows lava flows erupted during the 1983-present activity of Pu`u `O`o and
Kupaianaha. The flows active from mid-December 2000 through 22 March 2001,
above and on Pulama pali and on the coastal plain, are shown in red. Most of the recent flows are fed from
breakout points at 1920-1700 feet, above the pali in the northern part of the large red area.
Lava re-entered the sea just west of Kamokuna on January 21, 2001, but soon stopped when activity
shifted from the western to the eastern branch of the flow. Since then, activity
has been divided between the eastern and western branches. Breakouts from the
eastern tube system have destroyed hundreds of meters of the Royal Gardens
access road. Lava fed through the eastern system has been entering the ocean
since April 25, a few hundred meters northeast of Kupapau Point. On May 31, a
tiny trickle of lava fed through the western tube system dripped into the water
about 500 m west of the Kamokuna bench.
Eruption-viewing opportunities change constantly, refer to the HVO home page for
current information. Those readers planning a visit to Kilauea or Mauna Loa volcanoes can get much useful
information from Hawai`i Volcanoes National Park.
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